Hydro Pump Problem

This is on a Hustler 260K it has a Sunstrand pump. I bought this machine used and not running, has approx 1100 hours on it. The control lever on the right side seems to be binding compared the the left lever. When I first engage the pump clutch the engine bogs down and almost stalls out for a few seconds then speeds up and everything seems to work good. I notice if I first back off the screw that you loosen on the pump to allow the machine to be easily pushed, the control lever moves easily and the engine does not bog down when engaging the clutch. I can tighten up this screw with the clutch engaged, engine running and all seems fine after that till the next time I start the engine.

the screw I am referring to is actually called the "tow valve". The pump is a Sunstrand model 15. This morning I tried it again. When engagine the pump clutch the motor running at full throttle would completely stall out. It took 4 tries with the engine running at top speed, stalling each time, until the pumps were up and running. Once everything was spinning the machine operated normally, I operated it for at least 20 minutes up and down the driveway and it went great in all directions. Nothing appeared overly hot or noisy.

you guessed it. It took me a while but thats what I found. It is a Vanguard 20HP motor, I thought it was running too smooth to be misfiring but when I disconnected the right plug wire the engine ran exactly the same. It has very random spark and good compression so I've got to chase down a coil for it now.

and installed it, no change. I found the the wiring assembly for the stop switch with the built in Diodes was bad shorting out the #1 cylinder. The local dealer had the wire in stock. I got the motor running perfect now and the Hydrostatic drive works perfectly, the motor barely notices it when I engage the pump clutch now.